Note that QCad 2.1.6.4 comes with an SVG export function. It's not meant for further processing but for presentation only (everything is broken up in lines). We use SVG export in connection with XSL-FO / Apache Fop here.

Actually SVG export (with QCad of course) makes an excellent front end for Cheetah3D, a solid modeller package for Mac OS X. I and a few others are hoping that Martin Wengenmayer, C3D's developer will make C3D more architecturally friendly (at the moment, it C3D is better suited to game modelling).